The broad objective of the research proposed in this competing continuation application is to identify predictors of risky and safer sexual behavior and sexually transmitted disease (STD) among South African adolescents. This is a collaborative effort by a multidisciplinary team of researchers from the United States and the Republic of South Africa to conduct a long-term follow-up of an ongoing clustered randomized controlled trial of an HIV/STD risk-reduction behavioral intervention. The Specific Aims are to (1) determine whether the effects of the HIV/STD risk-reduction intervention on self-reported sexual behavior are evident at 36-month and 48-month follow-up;(2) determine whether the intervention reduced the rate of clinically documented STDs;(3) identify participants'characteristics and theoretical mediator variables assessed at baseline that predict sexual-risk behavior at long-term follow-up;and (4) identify participants'characteristics and theoretical mediator variables assessed at baseline that predict STD incidence. The participants will be the 1,057 Xhosa-speaking grade 6 learners from the 18 schools in Mdantsane and Berlin in the Eastern Cape Province, South Africa who were randomized to Let Us Protect Our Future a 12-hour HIV/STD Risk- Reduction Intervention or a 12-hour health-promotion control intervention on health issues unrelated to sexual behavior. Male and female Xhosa-speaking co-facilitators from the community led both interventions. The theoretical basis of the interventions was social cognitive theory and the theory of planned behavior. Extensive formative research, pilot studies, and input from a Community Advisory Board were employed to ensure the contextual appropriateness of the interventions and other protocols. The participants will be about 16 years of age at the time of the proposed 48-month follow-up, an age at which many South African adolescents have their sexual debut. The proposed research, then, provides a unique opportunity to examine predictors of sexual risk behavior at a critical period in the development of South African adolescents. Confidential self-report questionnaires will be employed to assess sexual risk behaviors and theoretical variables hypothesized to mediate the intervention's effect on such behavior 36 months and 48 months postintervention. Urine specimens will be collected and tested for Chlamydia trachomatis, Neisseria gonorrhea, and Trichomonas vaginalis using DNA-amplification technology. To address the Specific Aims, we will analyze the data with generalized estimating equations (GEE) and random effects models. The results of this study will contribute to scientific knowledge regarding the long-term effects of HIV/STD risk- reduction interventions for South African adolescents and the predictors of sexual risk behavior and STD rates as the participants approach middle adolescence.